Fluidized bed drying is a well-known chemical process technique. Briefly, it may be described as a method wherein a flowing gas (usually heated) suspends a bed of granular material which is being dryed. The system is reported to have high thermal efficiency due to the intimate contact of the drying gas with the wet particles.
Fluidized bed drying is useful for drying a wide variety of products. For example it has been used to dry polymers, such as polyacrylonitrile, polycarbonate, polyethylene polyvinyl acetate, polyvinyl chloride and ureaformaldehyde resin; also, it has been used to dry chemicals such as ammonium sulfate, sodium sulfate, and boric acid; further, it has been used to dry pharmaceutical products, still further, it has been used to dry foodstuffs, such as baby food, salt, sugar, coffee, cocoa mixtures, and coffee whiteners; moreover, it has been used to dry materials such as sawdust, sand and grains.
While fluidized bed drying has been used to dry polyvinyl chloride, some problems are present in this use due to the tendency for the resin particles to agglomerate. One means of overcoming this problem is disclosed in U.S. Pat. No. 3,494,046. This patent solves the problem by use of an improved fluidized bed drying apparatus.
My invention provides a solution to the problem of fluidized bed drying of particulate matter and particularly the type which is subject to agglomeration. Moreover, my invention does not require a particular type of apparatus as the dryer.
Briefly, my invention comprises adding an effective amount of a fluidizing agent, as described hereinafter, to the particulate matter prior to drying.